Personal audio devices, including wireless telephones, such as mobile/cellular telephones, cordless telephones, mp3 players, and other consumer audio devices, are in widespread use. Such personal audio devices may include circuitry for driving a pair of headphones or one or more speakers. Such circuitry often includes a power amplifier for driving an audio output signal to headphones or speakers. Oftentimes, such power amplifier is implemented using a transconductance with capacitances feedback compensation (TCFC) amplifier.
In many instances, power supplies used to provide electrical energy to amplifiers may be noisy, including having significant high-frequency noise (e.g. mid-band noise in the range of 100 KHz to 1 MHz). In many traditional approaches, such high-frequency noise may mix with out-of-band noise (e.g., quantization noise of a delta-sigma modulator used to implement a data converter) and fall within the audio band. Poor power supply rejection ratio at such frequencies may result in variation of an input signal to be amplified in order to compensate for noise-induced current, and such supply-induced noise at the input may mix with incoming high-frequency noise (e.g., modulator-shaped quantization noise), and may fold in-band, this raising a noise floor and degrading dynamic range of an audio system.